Well, maybe the singing part isn't necessary. Natalie Wood didn't sing Maria's songs (or at least it isn't her voice that made into the final soundtrack of the movie). :P

Richard Beymer's (Tony) songs were actually sung by someone named Jimmy Bryant. Beymer was great in Twin Peaks as dirty dealer Benjamin Horn. Russ Tamblyn, now 71, was also in Twin Peaks as the loopy Dr. Lawrence Jacoby.